March 7, 2014
More good news from astronomers hunting exoplanets! After Kepler mission confirmed 715 planets last week, another 8 have been discovered orbiting red dwarf stars. Eight might not seem like an impressive number, but the significance of the discovery could turn out to be far-reaching.
Artist's impression of a super-Earth. Credit: NASA, ESA, D. Aguilar (CfA)
By combining data from two planet surveys, the HARPS (High Accuracy Radial Velocity Planet Searcher) and UVES (Ultraviolet and Visual Echelle Spectrograph), both operated by European Southern Observatory, a team from the University of Hertfordshire, UK and Chile managed to confirm eight new exoplanets, all orbiting red dwarf stars.
Three of those are super-Earths orbiting their stars in habitable zones. Super-Earths are exoplanets slightly more massive than Earth, while a habitable zone represents the distance range around the star where the water can remain liquid and support life.
More significant than finding eight new exoplanets, even more significant than three of those being super-Earths in habitable zones is the implication that all red dwarfs have at least one exoplanet orbiting them.
HARPS and UVES that on their own are very successful at finding planets, but signals from sources observed were simply too weak for any of them to detect individually.
"We were looking at the data from UVES alone, and noticed some variability that could not be explained by random noise," said Dr Mikko Tuomi from the University of Hertfordshire's Centre for Astrophysics Research. He is the lead author of the new study. "By combining those with data from HARPS, we managed to spot this spectacular haul of planet candidates."
When detecting planets using radial velocity method, like this study, astronomers look for wobbles of host stars caused by their planets' gravitational pull. The smaller the planet is, the weaker its gravitational pull, which makes it understandable why these new eight low-mass planets were only found after combining HARPS and UVES, but not before additionally applying a new analysis techniques and filtering excess noise in measurements.
Newly discovered exoplanets orbit red dwarfs that are 15 to 80 light-years away from us, so they are actually pretty near. Their distances from their host stars range from 0.05 to 4 astronomical units – distance between Earth and Sun, about 149 million kilometers.
"We are clearly probing a highly abundant population of low-mass planets, and can readily expect to find many more in the near future – even around the very closest stars to the Sun," Tuomi added.
The tally of known exoplanets around red dwarfs is now 25, soon to be even more if any of 10 additional, even weaker sources detected by this study turn out to be new planets.